1. The alloy, in numbers
Cobalt chrome is a cobalt-chromium-molybdenum alloy. The chromium is what matters biologically: it oxidises at the surface to form a thin, self-repairing Cr2O3 passive layer, and that layer is the reason the alloy tolerates the oral environment. Molybdenum refines the grain structure and improves strength. Cobalt does the balancing.
Typical commercial composition for RPD frameworks:
Element | Typical range | What it does |
|---|---|---|
Cobalt (Co) | 60–65% | Matrix metal; contributes hardness and stiffness |
Chromium (Cr) | 25–30% | Forms the Cr2O3 passive layer that gives corrosion resistance |
Molybdenum (Mo) | 5–7% | Grain refinement and strength; improves castability |
Composition figures follow the ranges published in dental materials research and summarised in removable partial denture framework materials guides. Always confirm the specific alloy and whether it contains nickel or beryllium on the certificate we ship with the case — high-nickel or beryllium-containing variants exist and are not interchangeable with the composition above.
1.1 Physical and mechanical properties
Property | Cobalt chrome | Titanium | PEEK |
|---|---|---|---|
Tensile strength | ~700 MPa | 345–950 MPa (grade dependent) | ~100 MPa |
Elastic modulus | ~210 GPa | ~110 GPa | ~3.6 GPa |
Vickers hardness | 350–450 HV | lower than Co-Cr | very low |
Density | 8.5 g/cm³ | 4.5 g/cm³ | ~1.3 g/cm³ |
Behaviour at thin sections | stiff, holds shape | lower stiffness | flexible |
Values are drawn from a removable partial denture framework materials guide.
Two things follow from that table, and they pull in opposite directions.
Stiffness is an advantage and a nuisance. A modulus around 210 GPa means a thin cobalt chrome section barely flexes, so rests stay seated and the frame transmits load predictably. It also means the framework feels heavy. Density of 8.5 g/cm³ is nearly double titanium's 4.5 g/cm³, and that is the physical reason upper cobalt chrome frameworks can feel less secure than their acrylic counterparts — weight works against retention and against the patient's sense of control. If a patient complains that a denture "feels loose", the material is sometimes the first suspect and the fit is the second. Titanium is the usual answer when minimum weight matters more than a thin, rigid connector; a comparison of chrome cobalt and titanium partials covers the trade-off in more detail.
Hardness cuts both ways. 350–450 HV resists deformation and wear of the frame, but it is also a rigid, unforgiving surface at the abutment. That is why a rest seat has to be prepared to a defined form and clearance, and why we ask for the design to be approved on the digital drawing before anything is cast. See section 4.
2. Casting or SLM: which route, and why it matters to you
The same alloy reaches the clinic by two fundamentally different routes, and they are not interchangeable in cost, tolerance or turnaround.
Cast framework | SLM (selective laser melting) | |
|---|---|---|
How the frame is formed | Wax pattern invested, burnt out, alloy cast into the mould | Built layer by layer from metal powder under laser |
Rest seat fit to abutment | Studies report up to 76% of cast frames miss a 0–50 µm close fit | Fit reported in the 20–100 µm range |
Frame weight | Standard weight | Around 60% lighter than cast equivalents |
Cost per unit | Lower | Higher |
Best suited to | Cost-sensitive cases, broad indications | Thin sections, limited interocclusal space, high-value cases |
The fit and weight figures come from clinical comparisons of SLM cobalt chrome partials and SLM manufacturing reports, with underlying fit accuracy data in peer-reviewed research and SLM vs casting retention studies.
Read the table honestly: SLM is better on fit and longevity, and it costs more. It is not "better dentistry" in every case. Where there is comfortable occlusal space and the case is uncomplicated, a well-executed cast frame is a perfectly good outcome.
If interocclusal space is tight, say so early. A cobalt chrome framework needs roughly 1–1.5 mm of clearance for the metal components; the exact figure depends on which connector and rest design you choose. If the patient does not have that room, no process will rescue the case, and material changes may need to be discussed at the design stage rather than discovered at fit. We measure the space on the model and report back rather than assume it.
3. Where cobalt chrome is the right call
A cobalt chrome partial is strongest when the remaining teeth can carry it and the intervening span is being restored.
Indications that favour it:
- Class I, II and III partially edentulous cases with a bounded span and usable abutments
- Patients needing high chewing loads supported over a long span
- Patients who are not suitable candidates for a full-coverage fixed solution, or who want a removable solution that can still be modified later
- Long-span cases where a thin, rigid framework avoids loading the abutments excessively
Situations that need care or a different route:
Situation | Why it complicates things |
|---|---|
Very deep undercuts on abutments | Limits clasp selection and path of insertion; may push you toward a different approach |
A single isolated missing tooth with no adjacent support | An RPD adds complexity for little benefit; a bridge or implant may serve better |
Significant ridge resorption in an upper arch | Full-palate metal frameworks are harder to retain simply because they are heavy; the upper arch may be better served by an acrylic or flexible design |
Little interocclusal clearance | Metal thickness cannot be reduced without compromising strength; consider a thinner material or design change |
Nickel or beryllium sensitivity | Certain Co-Cr variants contain these; confirm the alloy certificate before use |
Where a case is a poor cobalt chrome candidate, we say so before you commit — you are welcome to take that advice to the patient rather than have it discovered at the delivery appointment.
4. Design sign-off: what has to be confirmed before we start
This is the section that saves you the most rework. Most returns we see are not manufacturing errors; they are design decisions that were never confirmed by the clinician. Below is what we ask for on a cast framework case, and why.
Information we need | What it controls | What happens if it is missing |
|---|---|---|
Surveyed model or intraoral scan | Undercut measurement, path of insertion | We cannot survey; the framework cannot be designed safely |
Survey line / path of insertion decision | Which surfaces a clasp can engage | Wrong path locks the frame in or lets it fly out |
Abutment preparation and rest seat design | How vertical load transfers to the tooth | Premature contact, rocking denture, possible abutment wear |
Clasp type and position per abutment | Retention versus aesthetics versus occlusal interference | Visible clasps, or a clasp that gets in the way of eating |
Rests, minor connectors, major connector choice | Structural continuity and force distribution | Structural risk in the finished frame |
Mesh or lattice retention for the resin saddle | Mechanical lock between metal and acrylic | Saddle delamination over time |
Shade selection | Tooth match to the remaining dentition | Patient dissatisfaction that no amount of adjustment fixes |
Opposing dentition | Clearance and occlusal load assessment | High contacts we cannot polish away |
How we handle sign-off. For a framework that requires design approval, the framework design is drawn digitally and sent to you for approval before casting or milling. Clasp types (for example circumferential or I-bar), rest positions, connector dimensions and the extent of the retention mesh are annotated on that drawing, so what you approve is what gets made.
4.1 Things worth confirming for the patient conversation
A few items belong in the treatment discussion rather than in the lab order, because they are clinical decisions, not manufacturing ones:
- Shade. Provide a shade reference (A1–D3 range or equivalent). It is the single most common reason a patient is dissatisfied with an otherwise technically sound denture.
- Clasp visibility. Where aesthetics matter, state which surfaces you are willing to show a clasp on and which you are not. That constraint shapes the entire framework design.
- The patient's existing denture. If they are being converted from an acrylic partial, sending the existing denture lets us match the tooth arrangement they are used to.
- Expectations about weight. Cobalt chrome is heavier than acrylic. Patients who have just transitioned from an acrylic partial should be told this in advance. Explaining the specific mechanics — why a heavy metal frame feels different in the palate — matters more than a vague "it will feel different".
4.2 Repair, reline and modification
One of the arguments for a cast metal framework is that it can be modified. Adding teeth to an existing cobalt chrome frame later is feasible provided the mesh retention area is designed in from the start. If the mesh was omitted or sized for a single tooth only, later additions are much harder, and in some cases the frame has to be remade. Worth specifying up front if you expect the case to change.
5. Cobalt chrome vs the alternatives
A short comparison table is more useful than a paragraph of adjectives, so here is one. All comparisons are directional; the exact figure depends on the specific product.
Dimension | Cobalt chrome | Acrylic (PMMA) | Titanium | Flexible nylon (Valplast) |
|---|---|---|---|---|
Rigidity | Very high | Low | High | Low |
Density | 8.5 g/cm³ | ~1.2 g/cm³ | 4.5 g/cm³ | ~1.1–1.2 g/cm³ |
Thin-section strength | Excellent | Poor | Excellent | Good |
Chairside repair | Not possible | Easy | Not possible | Difficult |
Add teeth later | Possible if mesh designed in | Easy | Possible | Difficult |
Rigidity under load | Holds shape | Can flex/warp | Holds shape | Can deform |
Metal allergy risk | Low if Ni/Be-free | None | Very low | None |
Cost | Moderate | Lowest | Highest | Moderate–high |
A note on density for PEEK. Some sources quote PEEK at around 1.3 g/cm³; the figure depends on the grade. The key point is that it is a polymer and sits in the acrylic range, not the metal range.
6. Delivery specifications, turnaround and quality
Everything in this section is our own specification, and we would rather you check it against your own records than take our word for it.
Specification | Value |
|---|---|
Turnaround (days in lab) | 5–7 working days for cast framework cases |
Turnaround | 3–5 working days for SLM framework cases |
Turnaround | 2–3 working days for a simple tooth addition / reline in an existing cobalt chrome frame |
Freight | DHL, FedEx, UPS or SPIDER (France) |
Freight cost | Outbound freight is the client's; return freight is covered by us above a certain parcel value |
Freight account | We can ship on our own carrier account, and factory-volume agreements apply |
Packaging | Each case individually bagged and boxed with foam protection; no branding on standard packing |
Packaging | Multiple cases can be consolidated into one shipment |
Notification | Design complete, production complete and dispatch notifications, with tracking number |
Notification | Case status is queryable at every stage |
Design revisions | One design, two revision rounds included |
Revision policy | Changes requested after design approval may affect cost and lead time |
Turnaround is counted in working days and starts on receipt of complete case materials. Time spent waiting on design approval, missing paperwork or your reply is excluded and the clock restarts once materials are complete. Chinese public holidays are not worked and are not counted.
6.1 Quality control
Removable prosthetics are inspected at four separate points rather than at the end. The logic is that a defect caught at the framework stage costs nothing, while the same defect caught at the finished stage costs a remake.
Model verification — the model or scan is checked against the prescription before design begins.
Wax try-in and arrangement check — tooth position, midline, arch form and occlusion verified.
Injection / packing stage check — internal defects, bubbles and thickness verified before finishing.
Final inspection — occlusion (centric, protrusive, lateral, with premature contacts removed), arrangement (midline, curvature, overjet/overbite), base thickness and extension, clasp fit and retention, and surface finish (smooth, no scratches or burrs), checked against the approved prescription and design.
Final release is made by quality control staff who do not make the product. The QC role is independent of the technicians, and release is against the confirmed prescription and our internal standard. Photographs of the finished case can be provided on request.
6.2 Repairs, relines and additions under an existing frame
Cases sent to us for repair, reline, rebase or tooth addition under an existing cobalt chrome frame go through a specific set of steps:
Step | Detail |
|---|---|
Case intake | We need upper and lower models, the existing denture/base, and a wax rim record |
Shape and occlusion capture | Impression or scan of the surrounding teeth; occlusion and vertical dimension recorded on wax |
Repair reason agreed first | We confirm the reason for the repair before modifying, so we do not change something you did not intend |
Repair scope | Shade, surface finish, minor form and contacts can be adjusted |
Inspected and returned | The internal surface receives only light finishing to avoid altering fit |
Rush handling | Rush repairs are prioritised, typically 3–5 days |
The upper and lower models, the old base and a wax rim record are required. Without them we cannot reproduce the vertical dimension or the occlusion.
7. FAQ
What is the difference between chromium cobalt and cobalt chrome?
Nothing material. They are the same cobalt-chromium alloy. Chromium cobalt is the common term in some markets and catalogues; cobalt chrome is standard in US and UK labs and in most clinical charts. Use whichever your supplier uses — the alloy certificate is what matters.
How long does a cobalt chrome partial take to make?
5–7 working days in the lab for a cast framework, 3–5 for SLM. Working days only, starting from receipt of complete materials, and excluding time spent waiting on design approval or your reply.
Can I add teeth to an existing cobalt chrome denture later?
Yes, provided the mesh retention area was designed in from the start. If it was not, the addition is much harder and sometimes the frame has to be remade. Worth specifying when you send the original case.
Is cobalt chrome suitable for patients with metal allergies?
Most cobalt chrome alloys used for RPDs are nickel- and beryllium-free, but variants exist. Confirm the specific alloy certificate. If you need a metal-free option we can supply PEEK or a flexible nylon design, though both have their own limitations.
Will a cobalt chrome denture feel heavy?
It usually does. Cobalt chrome is nearly twice the density of titanium and considerably heavier than acrylic. The rigidity is an advantage for load distribution, but the weight works against retention and comfort. Where weight dominates, discuss titanium.
Can a cobalt chrome partial be adjusted or repaired chairside?
Not the way acrylic can. The frame cannot be bent chairside and teeth cannot be added at the chair. Both go back to the lab.
How many patient visits does this take?
Typically three: preparation and final impression, a try-in to approve tooth arrangement, and the delivery appointment. Where design sign-off happens on a digital drawing, the framework design approval does not add a patient visit.
What happens if the framework does not fit at fit-in?
Contact us within 24 hours with the case number and photographs. We confirm the cause first, then adjust or remake. Factory-side quality issues — a base that does not seat, a lifted edge, an unreasonable clasp position, inaccurate occlusion or a shade mismatch — are reworked at no charge for labour. Freight and components are not covered.
Does a cobalt chrome partial need to be removed at night?
Removing a partial denture at night and cleaning it daily is standard advice for any removable appliance, and it applies here. Clean it with a brush and a non-abrasive cleaner, and avoid hypochlorite-type cleaners on metal components.
8. How we work with you
If you are a clinic or a solo dentist. Send the model or scan with a shade reference and your design notes. We will come back with the framework design drawing for approval if the case needs one, then manufacture, inspect and ship. Most cases are a single exchange.
If you are a partner lab. We can take on framework overflow, work from your design files, and ship under your own labelling and packing instructions. Standard packing carries no branding, and we can follow your own naming, labelling and shipping standards.
Factory visits. Our facilities are in Shenzhen and Huizhou, China. We welcome visits, production line tours, video inspections and capability discussions — just arrange it with your account manager.
Send us a case. Contact your account manager with the model or scan, the shade reference and the case details. If you are not yet set up with us, tell us what you need and we will send the material list and price list, and answer the technical questions directly.